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<h3>Explanation</h3>
The Stefan-Boltzmann Law gives the energy radiation <em>per unit area</em> of a black body:

where,
the total power emitted,
the surface area of the body,
the Stefan-Boltzmann Constant, and
the temperature of the body in degrees Kelvins.
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Keep as many significant figures in
as possible. The error will be large when
is raised to the power of four. Also, the real value will be much smaller than
since the emittance of a human body is much smaller than assumed.
Answer:
A - Crest, B - amplitude, C - wavelength, D - trough
Explanation:
Amplitude is a measurement of the magnitude of displacement (or maximum disturbance) of a medium from its resting state, as diagramed in the peak deviation example below (it can also be a measurement of an electrical signal's increased or decreased strength above or below a nominal state).
Reduce friction because friction just makes things harder